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Publication numberUS3755208 A
Publication typeGrant
Publication dateAug 28, 1973
Filing dateOct 23, 1970
Priority dateOct 23, 1970
Publication numberUS 3755208 A, US 3755208A, US-A-3755208, US3755208 A, US3755208A
InventorsH Ehrenfreund
Original AssigneeHaskon Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Avoidance of cell collapse in an extrusion process for a copolymer based on a low molecular weight {60 -olefin and polar vinyl monomer
US 3755208 A
Abstract
Post extrusion cell collapse of vinyl copolymer foams is prevented by incorporation of a small amount of a partial ester of a long chain fatty acid and a polyol.
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Description  (OCR text may contain errors)

United States Patent DIG. 5, DIG. l3

'Ehrenfreund Aug. 28, 1973 1 AVOIDANCE OF CELL COLLAPSE IN AN [56] References Cited EXTRUSION PROCESS FOR A COPOLYMER UNITED STATES PATENTS BASED ON A Low MOLECULAR WEIGHT 3,644,230 2/1972 Cronin 260/2.5 E a-OLEFIN AND POLAR VINYL MONOMER 3,067,147 12/1962 Rubens et a1 264/53 X 3,222,304 12/1965 Ingram 260/2.5 R [75] Inventor g Ehrenfremd 3,177,174 4/1965 Tirpak 260/3l.6 x 3,461,088 8/1969 Stahnecker et a1. 264/53 x [73] Assignee; Haskon, Inc Wilmington, DeL 3,541,040 11/1970 Eastes et a1 260/31.6 22 Filed: 061.23, 1970 OTHER PUBLICATIONS Lasman, Henry R. Blowing Agents. Wilmington, [21] Mass., National Polychemicals, Pages 547-550. (Re- Related US. Application Data printed from Encyclopedia of Polymer Science and [63] Continuationin-part Of Ser. N0. 706,612, Feb. 19, Technology. Q 2, Pages 532-565,

1968, abandoned.

Primary Examinen- -Philip E. Anderson [52] US. Cl 260/2.5 E, 260/23 H, 260/31.6, Attorney-Edwin H. Dafter 260/41 A, 260/86.7, 260/88.1 PC, 264/53,

264/DIG. 5, 264/DIG. 13 [57] ABSTRACT 2; gf 'f' g g jgg Post extrusion cell collapse of vinyl copolymer foams 1, 7 2; 88 1 2 is prevented by incorporation of a small amount of a partial ester of a long chain fatty acid and a polyol.

2 Claims, No Drawings AVOIDANCE OF CELL COLLAPSE IN AN 'EXTRUSION PROCESS FOR A COPOLYMER BASED ON A LOW MOLECULAR WEIGHT a-OLEFIN AND POLAR VINYL MONOMER This application is a -continuation-in-part of U.S. Application Ser. No. 706,612, filed Feb. 19, 1968 and now abandoned.

This invention relates to an improved process for the extrusion of foams of thermoplastic materials and to the foams produced thereby.

Small celled polymer foams are light-weight, low density materials which have many attractive commercial uses. In the past, most of this material has been prepared by compression molding or other techniques wherein foaming takes place within a confined volume, as in a shaping die. More recently the art has been moving in the direction of forming such foamed structures by extrusion since there are well known economic advantages to be realized from extrusion processes.

In the typical foam extrusion process, the polymer, with mixing aids, stabilizers, and other additives, is melted in the melting section of an extruder and an inert, low boiling hydrocarbon foamingor blowing agent is added thru the extruder barrel, under pressure, to the molten polymer. When the polymer is subsequently expolymers can be substantially reduced or eliminated if there is added to the polymer to be extruded 0.1 to percent by weight, based on polymer weight, of a partial ester of a fatty acid of about 12 to 18 carbon atoms and a polyol having 3 to 6 hydroxyl groups. The invention, then, is the improvement in the extrusion process for preparing foams of copolymers based on a low molecular weight a-olefin and a polar vinyl monomer using low boiling hydrocarbon blowing agents which comprises extruding such a copolymer having incorporated therein, in addition to the aforesaid hydrocarbon, 0.1 to 10 percent, preferably 0.1 to 3 percent, based on the weight of the copolymer, of a partial ester of a fatty acid of about 12 to 18 carbon atoms and a polyol having 3 to 6 hydroxyl groups.

The process of the invention is applicable to the preparation of foams of any copolymer based on a low molecular weight a-olefin and a polar vinyl monomer which can otherwise be employed in foaming processes. This includes, e.g., ethylene--vinyl acetate copolymer, ethyle'ne-ethyl acrylate copolymer, ethylene-- -vinyl chloride copolymer, and metallic salts of copolymers of ethylene and unsaturated carboxylic acids such as the zinc or sodium salts of ethylene--acrylic acid copolymer. Such materials are commercially available and can be used to prepare useful foam compositions. Foams of the above 'copolymers having extremely low bulk density, e.g., less than 10 pounds per cubic foot can readily be prepared using the process of this invention.

The partial esters of fatty acids which are used to prevent cell collapse of extruded polyolefln foams according to this invention are members ofa generic class known as surface active agents or surfactants. Exemplary surfactants in the class of useful additives include, for example, glyceryl monostearate, glyceryl distearate, mixtures of these monoand diglycerides, sorbitan' mono-, di-, and tri-oleates, and monoand diglycerides of oleic acid and palmitic acid, inter alia.

The reasons for theefticacy of the partial esters of the specified polyols in stabilizing foams is not known for certain. However, it has been postulated that there is a relationship between the solubility of the surfactant in hydrocarbons at low temperature and the ability to prevent foam collapse. It has been suggested that the surfactant must be at low temperatures in order to form a barrier to impede the escape of the hydrocarbon blowing agent from the polymer. This is not, however, intended as a limiting theory.

The blowing agent'which isemployed in the process of this invention can be any hydrocarbon which boils below the melting point of the polar copolymer. This includes such compounds as pentane, hexane, heptane, and octane. Also, halogenated hydrocarbons which meet the same limitations as to boiling point can be used as, e.g., methylene chloride, dichloroethane, chlorodifluoroethane, tetrafluoroetha'ne, and similar halogenated hydrocarbons. Mixtures of these materials'are also useful.

In addition to the specified surfactant and blowing agent, the foamable composition will also usually contain small amounts of a metallic soap such as zinc stea rate and a finely divided inorganic material such as calcium silicate as lubricants and cell nucleating agents. These materials are used in small amounts, e.g., a combined total of about 0.2 to 2 percent by'weight based on polymer weight. It is found that their presence contributes to the attainment of uniform small cell size in most cases.

By small cell foam, it is intended to indicate a foam having cells of about 2 millimeters or less average diameter. Cells of this small diameter are preferred since this type of foam is usually more resilient than one having larger cells. Additionally, smaller cells lead to smoother skin on the foam.

The extrusion of the foam is effected in any known way by means of either single ordouble screw extruders. Equipment of this type is standard and commer-- cially available, and forms no partbf this invention.

The improved process of this invention is applicable to the production of foamed articlesof any shape which can conveniently be formed by ext fusion, for example, sheets, rods, tubes, and wire or cable coatings. The resulting closed-cell foam structures are characterized by good thennal insulation'properties and light-weight.

In addition to the blowing agent, the polymer employed in this invention can, and usually will, contain other additives for other purposes, for example, a small amount of a heat or light stabilizer and an antioxidant -to prevent degradation during processing. Pigments,

EXAMPLE 1 A foamable composition was prepared containing 50 parts of a copolymer of about 93 percent ethylene and 7 percent vinyl acetate having a melt index of about 2, 0.2 part zinc stearate, 0.4 part calcium silicate and 0.4 part of a mixture of glycerol monoand distearate sold commercially under trade name Atmos 150. This mixture was extruded thru a 2-1/2 inch single screw extruder fitted with a round hole die. Temperature was controlled across the extruder in 5 zones and the die, as follows: first zone 166 C., second zone 160 C., third zone 157 C., fourth zone 157 C., fifth zone 1 16 C.; and at the die 88 C. Between the first and second zones, there was introduced 3.5 parts liquid hexane and 3.5 parts dichlorodifiuoromethane under pressure of 2850 psi.

On emerging from the die, the composition immediately expanded to a foamed rod about 0.77 inch in diameter. After cooling, this had shrunk to 0.70 inch and after 48 hours, was still 0.70 inch. The density of this foam was about 8.2 pounds per cubic foot.

When a control for the above test was run, omitting the glycerol monoand distearate mixture, the foam initially expanded to the same diameter, but upon cooling it shrunk to 0.60 inch and after 48 hours, it had further shrunk to about 0.45 inch. The density measured after 48 hours was about 13.2 pounds per cubic foot.

EXAMPLE 2 A composition similar to that of Example 1 was prepared containing 0.2 parts of glycerol monostearate in place of the mixed glycerides of Example 1, using hepv tane and dichlorodifluoromethane as blowing agents. The extruder in this instance was staged as follows: 165 C., 160 C., 154 C., 154 C., 116 C., and 92 C.

The resulting foamed rod had initial diameter of 0.75 inch, 0.70 after cooling and 0.70 after 48 hours. Its density was 8.1 pounds per cubic foot.

EXAMPLE 3 EXAMPLE 4 The foamable composition in this example was com prised of 50 parts of the sodium salt of a copolymer of about 90 percent ethylene with 10 percent acrylic acid, 0.4 part of the mixed glycerol diand monostearate, 0.4 part zinc stearate and 0.2 part calcium silicate. This was fed thru the same extruder and a mixture of 3.5 parts hexane and 7 parts dichlorodifluoromethane was added to form foamed rod. The extruder was temperature staged as follows: 166 C., 177 C., 154 C., 160 C., C., and at the die 88 C. The resulting foamed rod had initial diameter of 0.87 after cooling 0.82, and after 48 hours 0.82. lts density was 4.6 pounds per cubic foot.

EXAMPLE 5 A foamable composition was prepared containing 50 parts of a copolymer of 93 percent ethylene and 7 percent vinyl acetate, 5 parts of the sodium salt of ethylene--acrylic acid copolymer, 0.4 part of mixed glycerol monoand distearate, 0.25 part zinc stearate and 0.4 part calcium silicate. This was extruded thru a 2-1/2 extruder and a round hole die to form a foamed rod. The temperature profile of the extruder was 166 C.,160C.,l57C.,157 C., 116C., and 88 C., at the die. The resulting rod was about 0.60 inches immediately after extrusion, and about 0.55 after cooling. Its density was about 9.9 pounds per cubic foot.

EXAMPLE 6 The foamable composition in this example was cornprised of 50 parts of a copolymer of 8 percent ethyl acrylate-and 92 percent ethylene, 0.4 part sorbitan monooleate, 0.2 part zinc stearate and 0.2 part calcium silicate. This was extruded into foamed rods using the same extruder and same temperature profile as was used in Example 1 with 3.5 parts hexane and 7.0 parts dichlorodifluoromethane as the blowing agent. The foamed rod was 0.77 inch in diameter initially and shrunk to 0.70 inch on cooling. lts density was 8.6 pounds per cubic foot.

What I claim and desire to protect by letters Patent 1. In an extrusion process comprising: admixing in the extruder a copolymer selected from the group consisting of ethylene--vinyl acetate copolymer, ethylene-- -ethyl acrylate copolymer, ethylene--vinyl chloride copolymer-and the metallic salts of ethylene--acrylic acid copolymers, a low boiling blowing agent selected from the group consisting of (a) hydrocarbons, (b) halogenated hydrocarbons, and (c) mixtures of (a) and (b), and a nucleating agent comprising a finely divided inorganic material, the improvement of adding 0.1 to 10 rate.

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Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3067147 *Aug 28, 1957Dec 4, 1962Dow Chemical CoProcess of foaming and extruding polyethylene using 1, 2-dichlorotetrafluoroethane as the foaming agent
US3177174 *Dec 7, 1961Apr 6, 1965Grace W R & CoNon-static polyolefin-polyethylene glycol stearate ester composition
US3222304 *Nov 15, 1962Dec 7, 1965Koppers Co IncExpandable polyethylene
US3461088 *Jul 8, 1966Aug 12, 1969Basf AgProduction of expanded plastics moldings
US3541040 *Jun 28, 1968Nov 17, 1970Grace W R & CoAntifog polyolefin film
US3644230 *Feb 19, 1968Feb 22, 1972Haskon IncExtrusion process for polyolefin foam
Non-Patent Citations
Reference
1 *Lasman, Henry R. Blowing Agents. Wilmington, Mass., National Polychemicals, Pages 547 550. (Reprinted from Encyclopedia of Polymer Science and Technology, Vol. 2, Pages 532 565, 1965).
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3882209 *Jul 30, 1973May 6, 1975Furukawa Electric Co LtdMethod for extrusion coating electric wires with a foamed polyolefin resin involving reduced die-plateout
US3939237 *Apr 22, 1974Feb 17, 1976Asahi Dow, Ltd.Method of making a fluid transmitting porous tube or sheet
US4054550 *Apr 9, 1975Oct 18, 1977Monsanto LimitedProcess for producing cigarette filters
US4091136 *May 17, 1976May 23, 1978Shaw Plastics CorporationSynthetic cork-like material and method of making same
US4217319 *Dec 11, 1978Aug 12, 1980Japan Styrene Paper Corporation, Ltd.Process for producing polyolefin foams
US4327193 *Mar 6, 1981Apr 27, 1982Asahi-Dow LimitedDimensional stability of olefin polymer closed cell foams
US4359539 *Jan 22, 1982Nov 16, 1982Asahi-Dow LimitedFoaming synthetic resin compositions stabilized with certain higher ethers, esters or anhydrides
US4480054 *Jan 23, 1984Oct 30, 1984E. I Du Pont De Nemours And CompanyEthylene-(meth)acrylic acid interpolymer, polycarbonyl or polysulfone
US4521541 *Feb 9, 1983Jun 4, 1985International Flavors & Fragrances Inc.Perfumed resin for controlled release of animal repellant and diagnostic materials
US4839116 *Oct 24, 1985Jun 13, 1989Macgregor Golf CompanyMethod of molding a foamed core short distance golf ball
US5750584 *Jan 31, 1997May 12, 1998Knaus; Dennis A.Stability control agent composition for polyolefin foam
US5844009 *Apr 26, 1996Dec 1, 1998Sentinel Products Corp.Cross-linked low-density polymer foam
US5859076 *Jun 11, 1997Jan 12, 1999Sentinel Products Corp.Crosslinking; expansion; extrusion; compression molding; good cushioning properties and non-allergenic
US5874024 *May 11, 1998Feb 23, 1999Knaus; Dennis A.A stabilizer for inhibiting polymer shrinkage comprising at least one compound that is a partial ester of a fatty acid with polyol and at least one compound selected from higher alkyl amines or fatty acid amides
US5882776 *Jul 9, 1996Mar 16, 1999Sentinel Products Corp.Laminated foam structures with enhanced properties
US5883145 *Feb 25, 1997Mar 16, 1999Sentinel Products Corp.Cross-linked foam structures of polyolefins and process for manufacturing
US5929129 *Jul 12, 1996Jul 27, 1999Sentinel Products Corp.Crosslinked foamable compositions of silane-grafted, essentially linear polyolefins blended with polypropylene
US5932659 *Jun 21, 1996Aug 3, 1999Sentinel Products Corp.Single-site initiated polyolefin having a density below 0.878 g/cm3 and a polyolefin containing ethylene and propylene, a portion of the blend is crosslinked; no sulfur needed to cure; shapeable; replacement for conventional epdm; gaskets
US5938878 *Aug 16, 1996Aug 17, 1999Sentinel Products Corp.Polymer structures with enhanced properties
US6004647 *Jul 7, 1997Dec 21, 1999Sentinel Products Corp.Single-site catalyzed polyolefin resin having a density of below 0.878 g cm3 including ethylene and propylene, cross-linked; blends are formable and foamable
US6054005 *Apr 30, 1999Apr 25, 2000Sentinel Products Corp.Polymer structures with enhanced properties
US6103775 *Mar 16, 1999Aug 15, 2000Sentinel Products Corp.Silane-grafted materials for solid and foam applications
US6167790Oct 6, 1998Jan 2, 2001Sentinel Products Corp.Laminated foam structures with enhanced properties
US6214894Dec 21, 1999Apr 10, 2001Sentinel Products Corp.Crosslinking; molding materials
US6221928Nov 25, 1998Apr 24, 2001Sentinel Products Corp.Crosslinking polyolefin
US6242503Apr 28, 1999Jun 5, 2001Sentinel Products Corp.Crosslinking graft polymer; non-foamed, flexibility, nontacky
US6262137Jan 6, 1998Jul 17, 2001Sentinel Products Corp.Polymer articles including maleic anhydride and ethylene-vinyl acetate copolymers
US6316512Apr 24, 2000Nov 13, 2001Sentinel Products Corp.Silane-grafted materials for solid and foam applications
US6350512Sep 5, 2000Feb 26, 2002Sentinel Products Corp.Polyolefin tape from sheets
US6359021Apr 10, 2001Mar 19, 2002Sentinel Products Corp.Comprises crosslinked/formable resin of polyolefins of ethylene and propene based homopolymers and copolymers; foaming; gaskets; flexibility
US6472015May 5, 1997Oct 29, 2002Sentinal Products Corp.Cross-linked polyolefin tape
US6531520Jan 25, 2002Mar 11, 2003Sentinel Products CorporationPolymer blends used to make foam for floatation or for making gaskets.
EP0036561A2 *Mar 10, 1981Sep 30, 1981The Dow Chemical CompanyFoamable olefin polymer compositions stabilized with certain naphthyl amine compounds, foaming process using them and foam article produced
EP0036562A2 *Mar 10, 1981Sep 30, 1981The Dow Chemical CompanyFoamable olefin polymer compositions stabilized with certain higher ethers, esters or anhydrides, foaming process using them and foam article produced
EP0584276A1 Mar 24, 1992Mar 2, 1994Dow Chemical CoPerforated plastic foam and process for making.
Classifications
U.S. Classification521/79, 524/310, 524/110, 264/53, 521/149, 264/DIG.500, 524/456, 521/145, 524/317, 524/399, 521/908, 521/88, 521/91, 264/DIG.130
International ClassificationC08J9/00
Cooperative ClassificationC08J2323/02, Y10S264/05, C08J9/0023, Y10S264/13, Y10S521/908
European ClassificationC08J9/00K4
Legal Events
DateCodeEventDescription
Dec 13, 1985AS02Assignment of assignor's interest
Owner name: SEKISUI AMERICA CORPORATION, 100 WEST TENTH STREET
Effective date: 19851127
Owner name: VOLTEK, INC.
Dec 13, 1985ASAssignment
Owner name: SEKISUI AMERICA CORPORATION, 100 WEST TENTH STREET
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:VOLTEK, INC.;REEL/FRAME:004489/0137
Effective date: 19851127